A122542 → basis A013610 → basis A013611

nonnegative coefficients

Proved for all n all roots real, in (−∞, 0]coefficients of one sign Hadamard kernel interlacing (weak)

Recurrence

\(P_{n}(x) = \left(4 + 12\,x\right)\,P_{n-2}(x) + \left(5 + 12\,x\right)\,P_{n-1}(x)\)

\(P_{1}(x) = 1\)

\(P_{2}(x) = 4 + 12\,x\)

Rows ?

n	x⁰	x¹	x²	x³	x⁴	x⁵	x⁶	x⁷	P_n(1)
1	1								1
2	4	12							16
3	24	120	144						288
4	136	984	2304	1728					5152
5	776	7320	25344	38016	20736				92192
6	4424	51480	235584	528768	580608	248832			1649696
7	25224	349080	1984896	5927040	9787392	8460288	2985984		29519904
8	143816	2307096	15673536	58396032	128729088	167712768	119439360	35831808	528233504

All 15 rows

Technical details

Node id: n-35819491ecf79d70 · revision 0 · JSON
Definition source: derived:basis_map_A013611
Fingerprint: f6-dda21e41e51cc759

Observed on the stored rows ?

Degrees: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 (affine: slope 1, intercept -1)
Palindromic rows: no
γ-positive (gamma_positive): no
Nonnegative coefficients (nonn): yes
Only rational roots (rr_by_factors: every nonzero row is a product of linear factors over ℚ): no

Matches ?

No OEIS matches.

Submission text ?

Atlas rows n = 1, …, ascending powers of x

%e Example

Triangle begins:
   1:       1;
   2:       4,       12;
   3:      24,      120,       144;
   4:     136,      984,      2304,       1728;
   5:     776,     7320,     25344,      38016,       20736;
   6:    4424,    51480,    235584,     528768,      580608,      248832;
   7:   25224,   349080,   1984896,    5927040,     9787392,     8460288,     2985984;
   8:  143816,  2307096,  15673536,   58396032,   128729088,   167712768,   119439360,    35831808;
   9:  819976, 14960280, 118181376,  527589504,  1454671872,  2534602752,  2723217408,  1648263168,   429981696;
  10: 4675144, 95595288, 860809536, 4477790592, 14820102144, 32344676352, 46521630720, 42496524288, 22359048192, 5159780352;

%F Formula

The row polynomials satisfy P(n,x) = (4+12*x)*P(n-2,x) + (5+12*x)*P(n-1,x) for n >= 3, with P(1,x) = 1, P(2,x) = 4 + 12*x.

%t Mathematica

P[1, x_] := 1;
P[2, x_] := 4 + 12*x;
P[n_, x_] := P[n, x] = Expand[(4 + 12*x)*P[n - 2, x] + (5 + 12*x)*P[n - 1, x]];
Table[CoefficientList[P[n, x], x], {n, 1, 10}] // Flatten

%o PARI/GP

P(N) = {my(v = vector(N)); v[1] = 1; v[2] = 4 + 12*x; for(n = 3, N, my(i = n); v[i] = (4 + 12*x)*v[i - 2] + (5 + 12*x)*v[i - 1]); v};
row(n, p) = {my(c = Vecrev(p)); c};
T(N) = {my(v = P(N)); concat(vector(#v, i, row(i, v[i])))};
T(10)

polytool c48629374597

Properties

Real-rooted? Every row P_n, n ≥ 1, is zero or real-rooted with all roots in (−∞, 0]
by Geometric basis map (elementary)
Coefficients of one sign? Every nonzero row, n ≥ 1: the coefficients of P_n have one sign
derived from Geometric basis map (elementary)
Hadamard kernel (Malo)? Rows P_n, n ≥ 1, are Hadamard kernels (preserve real-rootedness)
derived from Geometric basis map (elementary)
Interlacing of consecutive rows? Rows P_(m-1), P_m interlace (weak, unordered) for every m ≥ 2
by Geometric basis map (elementary)

Proof chains ? JSON

Geometric basis map (elementary) polytool ? step ›
- from basis_map_A013610 of Triangle T(n,k), 0 <= k <= n, read by rows, given by [0, 2, -1, 0, 0, 0, 0, 0, ...] DELTA [1, 0, 0…?
  - Geometric basis map (elementary) polytool ? step ›
    
    from Triangle T(n,k), 0 <= k <= n, read by rows, given by [0, 2, -1, 0, 0, 0, 0, 0, ...] DELTA [1, 0, 0, 0, 0, 0, 0, 0, ...]…?
    
    Liu–Wang theorem for three-term recurrences [LW07, Thm 2.1, Thm 2.3, Cor 2.4, Prop 3.3] polytool ? step › direct check
    
    Liu–Wang theorem with a lag row [LW07, Thm 2.1] RealRooted ? step › direct check
  - Geometric basis map (elementary) polytool ? step ›
    
    from Triangle T(n,k), 0 <= k <= n, read by rows, given by [0, 2, -1, 0, 0, 0, 0, 0, ...] DELTA [1, 0, 0, 0, 0, 0, 0, 0, ...]…?
    
    ↑ Liu–Wang theorem for three-term recurrences (above)
    
    ↑ Liu–Wang theorem with a lag row (above)

References

[LW07] Lily L. Liu and Yi Wang. A unified approach to polynomial sequences with only real zeros. Advances in Applied Mathematics, 38(4):542–560, May 2007. doi:10.1016/j.aam.2006.02.003